Delayed Onset Ki Disorder is a disorder that greatly hinders a person's Ki.
This rare condition is the result of using one's ki in a reckless way, and presents its symptoms a few days after said usage. As a result, the users ki is greatly affected and only a fraction of the user's ki is able to be used. It is unclear how long it takes for it to heal, but the disorder will eventually cease in time. King Kai noted that if Goku continued to use his ki in a reckless way, he would not be able to become stronger, which greatly worried him.
In Goku's case, he was suffering from this disorder due to his usage of the Super Saiyan Blue Kaio-ken in the Universe 6 and 7 Gods of Destruction Selection Martial Arts Competition. Due to this disorder, Goku could barely control even a fraction of his ki, and has stated to Piccolo that if they were to fight all-out, Goku would lose. This disorder also affected Goku's flying, as he had unintentionally crashed into his house, destroying it. This disorder also affected his Instant Transmission technique, as it took Goku at least 4 tries to teleport to his destination, which was King Kai's planet. It is also worth mentioning that even though Goku's appetite is normally abnormally large, this disorder greatly reduced his appetite, as it worried Chi-Chi and Goten that Goku ended up eating less than half of his daily food intake.